The invention relates to a fitting for holding an end(s) of a section of corrugated tubing, whereby a seal is created. The resulting seal allows for a leak-free passage of gases and liquids.
Corrugated tubing is used in a wide variety of applications. Uses include gas lines for residential and commercial applications such as connecting a gas clothes dryer, water heater, kitchen range or central heating unit to a fuel source. Uses also include air conditioning systems, hydraulics, electrical applications, plumbing, and even medical applications such as delivering anesthesia products.
Corrugated tubing is often manufactured from metal, such as stainless steel, copper, aluminum and other metals, from plastics such as polyethylene, or a combination of metal and plastic. Additionally, corrugated tubing has ridges and grooves on its outer surface, which allow the tubing to bend.
The primary advantage of corrugated tubing is that it is flexible. Historically, rigid steel tubing was used for the transport of gases, particularly natural gas. However, rigid steel tubing is time consuming to cut, thread and tighten, and is often difficult to extend to remote locations. To bend rigid steel tubing, one must attach an elbow fitting to the straight sections of tubing. Flexible corrugated tubing, however, does not require elbow fittings and is, therefore, less expensive to install and able to reach locations that rigid tubing cannot. Further, flexible tubing has fewer locations where gases can leak than straight tubing equipped with elbow fittings. This reduces leak paths and pressure drops.
Corrugated tubing is generally attached to fuel sources, appliances, and additional sections of tubing through the use of couplings. Couplings lock the ends of the corrugated tubing restricting their movement providing a leak-free connection between the tubing and whatever the tubing is connected to. Couplings generally include a coupling body, a fastener such as a nut, and a sleeve that is received in a bore in the coupling body. A typical coupling is described in a patent to Fujiyoshi (U.S. Pat. No. 5,441,312).
One such coupling body has a threaded outer surface that receives the threaded inner surface of a nut. The coupling body also has an axial through bore into which the sleeve and tubing fits. The sleeve contains axial slits to divide the sleeve into segments. The sleeve also contains multiple ridges on its inner surface into which ridges on the outer surface of the corrugated tubing fit to secure the tubing to the sleeve. To use the coupling, first the tubing is inserted into the nut, then the sleeve is fitted over the end of the corrugated tubing so the ridges in the tubing fit into the ridges on the inner surface of the sleeve. A small portion of tubing projects from the end of the sleeve. The sleeve with the portion of tubing projecting is then inserted into the through bore of the coupling body. The nut is then threaded onto the coupling body and tightened causing the ridges on the portion of tubing projecting from the sleeve to be compressed. The compressed ridges create a seal between the end of the sleeve and the tube receiving inner seal surface of the coupling body.
The coupling described above, however, does not always create an adequate seal, as it is possible for the sleeve segments to misalign on the corrugated tubing and for the tubing to misalign on the inner seal surface of the coupling body. Furthermore, the sleeve in the above-described coupling should only be used once as it may be deformed upon tightening the nut.
Over the years, improvements have been made to couplings for corrugated tubing to make them somewhat easier to assemble and allowing one to reuse the sleeve. Another patent discloses a self-flaring, split bushing pipe coupling and hose assembly. This patent features a sleeve, or xe2x80x9csplit bushingxe2x80x9d that is comprised of at least two separate segments.
However, to assemble and use the coupling disclosed, one must perform multiple time consuming tasks. First, one must cut the tubing at a groove between convolutions on the surface of the tubing. The coating or jacket of the tube must then be cut back to reveal two convolutions on the surface of the tube. Then the nut is slid over the tubing and the sleeve or xe2x80x9csplit bushingxe2x80x9d is placed over the two exposed convolutions of tubing. The end of the tubing with the sleeve attached is then manually compressed by the installer and inserted into the coupling body and the nut is threaded onto the body and tightened creating a seal. This process takes approximately 10 minutes to complete in the field.
In addition to being time consuming, the assembly of the disclosed coupling may result in an inadequate seal under certain circumstances. The tube has to be manually installed into the coupling body such that the annular lip on the split bushing adequately fits into the tube corrugation. The size and shape of the split bushing rib must be manually reduced by the installer to accommodate the installation of the fitting components. If the tube corrugation is in some way misshapen, the split bushing may not fit properly and may not permit the fitting to be used; or it may allow the fitting to be used with a less accurate fit that could result in an inadequate seal.
Accordingly, there exists a need for a pre-assembled coupling that may be quickly and easily installed, that creates a strong, reliable seal that is resistant to overtorqueing and creates a strong seal with non-conforming corrugated tubing, and that may be easily reused.
The problems discussed above are alleviated by the fitting device disclosed herein. It is the object of the present invention to provide a fitting that is pre-assembled thereby reducing installation time and reducing the potential for contaminants to infiltrate the fitting during assembly.
It is a further object of the present invention to provide a fitting that provides a consistently reliable and strong seal that is resistant to overtorqueing and repeatedly creates a tight seal with corrugated tubing.
It is a further object of the present invention to provide a fitting that can be reused without disassembly.
It is a further object of the present invention to provide a fitting in which the sleeve is fully captured in the coupling body prior to installation.
It is a further object of the present invention to provide a fitting in which the sleeve is interchangeable with different fasteners and coupling bodies.
An exemplary fitting device disclosed herein comprising a coupling body, a sleeve, and a nut. One end of the nut has a through bore that is tapered and decreases in diameter toward the end of the nut. The outer surface of the sleeve is tapered as well which facilitates the radial movement of the sleeve segments upon tightening and locking the sleeve segments into the proper position on the corrugated tubing. The coupling body contains an inner seal surface with improved geometry that effectively concentrates the sealing load over a pre-determined surface and prevents overloading of the seal surface area. Specifically, an open relief surface adjacent to the seal surface in the coupling body prevents excessive or undesired crimping to the tube, which could result in fracturing the top edge of the crimped portion of the tube. Such a fracture could initiate a leak path.
The sleeve of the present invention is divided into four separate arcuate segments; the segments feature a spring. The spring is located on the interior of the sleeve. When the nut is tightened, all the sleeve segments are uniformly compressed properly fitting the sleeve rib into the tube corrugation. This prevents the sleeve from deforming upon further tightening the nut as do other sleeves that contain axial slits through only a portion of the sleeve. This also allows one to reuse the sleeve.
The spring on the inner surface facilitates the removal of the corrugated tube from the nut and coupling body by forcing the segments outward upon loosening the nut. This outward force allows the tubing to move free from the sleeve and out of the fitting device.
Additionally, the fitting device has several staked protrusions on the surface of the coupling body which function as a stop to prevent the nut from disengaging from the coupling body.
A heavy grease or xe2x80x9ccosmolinexe2x80x9d as is understood in the art, is preferably not applied to the assembled fitting because the grease will inhibit the movement of the pieces of the fitting and impede the mechanical function.